I can only comment on the 40CFE IF and 60CFI which i use with a P20. The 60 is cast free as far as i can see, and the 40 shows some colour fringing around some backlit areas when shot wide open to f5.6, both are super sharp. Incidently fringing can also occur wide open with my 100 & 180 however it's hardly noticeable, and gone one stop down.

The 40 CFE IF (latest) is the only wideangle lens i have tried (apart from some Digitars) which can equal or better the biogon for sharpness and contrast. After testing the new 40mm against my superwide SWCM, i sold the superwide, with my only grievance being the extra distortion apparent in the 40mm, and the extra 2mm.

I'm going to assume you are inferring to magenta/green color shift that is occurringacross the image and not fringing or chromatic aberration as Garry is responding to.

If this is the case then I think (bear in mind I don't own a DB but use them regularly) thatyou find this 'lens cast' evident,to varying degrees,in most wides (some have reported seeing it onHasselblad Apo Teles,as well) and near wides when using Phase backs.

There is a very simple 'fix' for this in Phases capOne software called,LCC correction.This involves taking an exposure with a translucent white disc placed over the lens in thesituation where you anticipate the cast occurring.You then open this file in C1 and neutralize the file using the LCC correction after whichyou apply this correction to all images taken with the same lens.Very quick and efficient once you run through it a couple of times.

These custom lens profiles are then stored within C1 and can be applied to images using the samelens under similar conditions.

I have seen the color cast with the SWC,as you have, the Arcbody with 45mm and anolder V 50mm blad lens.The presence of the cast,generally,diminishes with longer focal lengths

If you navigate your way to the Knowledge Base at PhaseOne.com you will find a muchcleared overview than I have provided here.

thnaks for the input, yes, i mean the yellow/green cast which appeared in the centre and changed towards the edges on my swc. i had assumed that this was due to the closeness of the lens to the sensor, hence the question on the retrofucus "wides" as the distance is further from the lens to sensor.